Until now many efforts have been developed, through the application of different techniques, to manufacture water cushions and water chairs, in an effort to get a chair providing the best possible comfort for the user, by offering maximum support for the lower part of the back or lumbar area, by minimizing the problem of waves, localized pressure points and the tightness, as well as the problem of bedsores of those patients prostrated or confined to a chair. Although there has been an advance in this kind of furniture, the above mentioned problems have not been properly solved since the current water furniture does not have a control mechanism for the pressure of the liquid contained inside the cushions, to assure that this pressure proportionally corresponds to the pressure that each part of the body exerts. Likewise, it has been not possible to reach a total flotation state.
In effect, until now, the current “water chair” consists of a structure with a cushion or cushions made of elastic or flexible materials, filled with a liquid element. The main idea is that, at the moment of receiving the weight of the user, the liquid contained in the seat cushion flows to the upper part cushion (the back); resulting in the same liquid being distributed between the cushions to support the whole body of the user.
It is true that the techniques developed so far have had some success; however, what has not yet been accomplished is the control of the different support pressures; nor a state of flotation without restraints.
In that way, for instance, we have the Ridder, Barbelet and Surber disclosures, U.S. Pat. Nos. 5,860,705; 4,929,026 and 4,738,486; respectively, which present just one envelope or cushion filled with liquid with two parts: Seat and back. In all these cases, the same principle is used: The seat part, when receiving the weight of the user, displaces the contained liquid towards the back cushion; thus the same liquid supports not only the seat but also the back of the user.
It has to be noted that in these inventions, the flow of liquid from the seat towards the back is not free, but limited or delayed by restriction mechanisms for the passing of the flow. Even though in the above mentioned patent documents it is claimed that the flow restriction mechanisms allow for the control of pressure; actually, such mechanisms only serve to avoid the abrupt changes or the waviness that is produced due to the effects of movement of liquid from one cushion to another, or from the seat towards the back; resulting in the same pressure, not only for the seat but also for the back cushion.
Likewise, the current water chairs are divided into two parts: seat and back; thus most are unable to give individual and controlled support for each main pressure point of the body of the user.
Another disclosure called: “Water cushion stress-reducing for chairs and other seating devices” developed by J. Sereboff, U.S. Pat. No. 4,761,011 refers to a fixed structure, prepared to hold a plurality of cushions horizontally disposed and vertically spaced, which are individually and partially filled with water. Although this invention has tried to give individualized support to different sections of the user's body, it has been unable to control the pressure or pressures for each support point of the body. Furthermore, due to the small volume of liquid used, it has been unable to make the user float comfortably on the chair.